Geodatabase topology comprises a collection of spatial rules that you can use to define relationships between features in a dataset. The workflow consists of defining a rule, validating the features, fixing errors, and marking exceptions.
Create a geodatabase topology
The first step includes creating a geodatabase topology for the dataset containing the features participating in the topology. You can right-click the dataset in the Catalog pane, or use the geoprocessing toolset.
Next, right-click the topology object, click Properties and click the Rules tab. Add the feature classes and the rules against which you want to validate them; for example, polygon features and a rule that requires that polygons must not have gaps.
In a map
Add the dataset and topology object to a map to validate feature topology and fix errors. The topology validation tools are available in the Modify Features pane and on the Error Inspector toolbar.
To learn more, see Validate and fix geodatabase topology.
Each geodatabase topology rule appears as a symbolized group layer with sublayers organized by geometry type showing errors, dirty areas, and exceptions. In the Error Inspector table viewer 
, errors and exceptions appear as line items.
The best practice to fix errors, is to first use the Fix Error tool 
. Clicking the nonconforming feature geometry shows a list of predefined tools for fixing the specific error. If a tool does not exist, you can fix an error using standard editing tools.